1. Field of the Invention
The invention is concerned with spinodal alloys.
2. Description of the Prior Art
Spinodal copper-nickel-tin alloys have been developed recently as commercially viable substitutes for copper-beryllium and phosphor-bronze alloys currently prevalent in the manufacture of articles such as electrical wire, springs, connectors, and relay elements. U.S. Pat. No. 3,937,638, issued to J. T. Plewes on Feb. 10, 1976, (Case 2) and assigned to the assignee hereof, discloses copper-nickel-tin alloys which, when cold worked and aged according to a critical schedule, exhibit unexpectedly high levels of yield strength in combination with high levels of ductility. For example, a copper-nickel-tin alloy containing 9% nickel, 6% tin, and remainder copper, when homogenized, cold worked by an amount corresponding to an area reduction of 99%, and aged for 75 minutes at a temperature of 300.degree. C, exhibits a yield strength of 182,000 pounds per square inch and undergoes 52% reduction in cross-sectional area under tension before failure.
The composition of these alloys is characterized in that such alloys are in a single phase state at temperatures near the melting point of the alloy but in a two-phase state at room temperature; the spinodal structure is characterized in that, at room temperature, the second phase is finely dispersed throughout the first phase rather than being situated at the first phase grain boundaries.
The treatment which develops the spinodal grain structure in preference to an undesirable second phase precipitation at the grain boundaries calls for homogenizing, cold working and aging the alloy. Specifically, the aging temperature is required to be in the vicinity of an optimal temperature T.sub.d dependent primarily on the amount of cold work performed but must not exceed the so-called reversion temperature T.sub.m which is dependent primarily upon the composition of the alloy. Table I taken from U.S. Pat. No. 3,937,638, shows reversion temperatures for a number of copper-nickel-tin alloys which develop a spinodal structure when properly cold worked and aged.